Department of Biology, Rhodes College, Memphis, Tennessee.
Hippocampus. 2020 Mar;30(3):233-249. doi: 10.1002/hipo.23152. Epub 2019 Sep 6.
The dorsal and ventral regions of the rat longitudinal hippocampal axis are functionally distinct. That is, each region is associated with different behavioral tasks and disease susceptibilities due to underlying anatomical, and physiological differences. These differences are especially pronounced in area CA1, where significant differences in morphology, synaptic physiology, intrinsic excitability, and gene expression have been reported between CA1 pyramidal neurons from the dorsal (DHC) and ventral hippocampus (VHC). However, despite a significant amount of recent attention, a cogent picture of the intrinsic electrophysiological profile of DHC and VHC neurons has remained elusive, due, in part, to experiments performed on rats at different developmental time points. Moreover, the resulting intrinsic electrophysiological profiles are sufficiently different as to warrant a thorough investigation of the spatial and temporal changes in the intrinsic excitability of CA1 pyramidal neurons across developmental time. Accordingly, in this study, I have characterized the intrinsic electrophysiological properties of CA1 pyramidal neurons from acute hippocampal slices prepared from the DHC and VHC throughout an approximately 3-week developmental period (P14-P37). DHC and VHC neurons exhibited distinct intra-region changes (DHC or VHC) and inter-region differences (DHC versus VHC) in their intrinsic electrophysiological properties, which yielded two developmental timelines: (a) a common developmental timeline describing changes observed in both DHC and VHC neurons, and (b) a differential developmental timeline highlighting unique features observed in DHC neurons. Specifically, DHC neurons exhibited significant inter-region differences in RMP, input resistance, threshold, and spike frequency adaptation relative to VHC neurons, as well as an intra-region change in the rebound slope (a proxy for I ). These observations both integrate and reconcile previous work performed with rats at different developmental stages and suggest a distinct developmental trajectory for DHC neurons that might shed light on the normal physiological functions and disease susceptibility of the DHC.
大鼠纵向海马轴的背侧和腹侧区域在功能上是不同的。也就是说，由于解剖和生理上的差异，每个区域都与不同的行为任务和疾病易感性相关。这些差异在 CA1 区尤为明显，在那里，已经报道了来自背侧（DHC）和腹侧海马（VHC）的 CA1 锥体神经元在形态、突触生理学、内在兴奋性和基因表达方面存在显著差异。然而，尽管最近引起了相当多的关注，但由于在不同发育时间点对大鼠进行的实验，DHC 和 VHC 神经元的内在电生理特征仍然难以捉摸。此外，由于内在电生理特征差异显著，因此需要对 CA1 锥体神经元在整个发育时间内的内在兴奋性的空间和时间变化进行彻底研究。因此，在这项研究中，我在大约 3 周的发育时间（P14-P37）内，从 DHC 和 VHC 的急性海马切片中描述了 CA1 锥体神经元的内在电生理特性。DHC 和 VHC 神经元在其内在电生理特性方面表现出明显的区域内变化（DHC 或 VHC）和区域间差异（DHC 与 VHC），这产生了两个发育时间表：（a）描述在 DHC 和 VHC 神经元中观察到的变化的共同发育时间表，以及（b）突出 DHC 神经元中观察到的独特特征的差异发育时间表。具体来说，与 VHC 神经元相比，DHC 神经元在 RMP、输入电阻、阈值和尖峰频率适应方面表现出明显的区域间差异，以及区域内的反弹斜率（I 的代理）变化。这些观察结果既整合了以前在不同发育阶段的大鼠上进行的工作，也调和了这些工作，表明 DHC 神经元具有独特的发育轨迹，这可能揭示 DHC 的正常生理功能和疾病易感性。
